<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <style>
    .parent{

        width: 500px;
        height: 500px;
        border: 1px solid #333;
        display: flex;
        flex-direction: column;
        /* flex-direction 属性为colum的时候 */
        /* justify-content: 控制垂直  
           align-items:   控制水平   */
        justify-content: space-evenly;
        align-items: center;

    }
    .parent>div{
            width: 100px;
            height: 100px;
            border: 1px solid #333;

    }
    
    
    </style>
    <title>Document</title>
</head>
<body>
    <div class="parent">
            <div></div>
            <div></div>
            
    </div>
</body>
</html>